The present invention relates to an apparatus for monitoring the environment of a prosthetic socket, and in particular to an apparatus for monitoring various parameters such as temperature, pressure, moisture, and vacuum, and for signaling the wearer of the prosthetic limb when one of these parameters exceeds a pre-set range.
A study conducted under direction of the Applicant/Inventor by Wayne J. Board in partial fulfillment for a Masters degree has shown that application of a vacuum on the expulsion port of a total surface-bearing socket to hold the liner tightly against the socket can prevent loss of residual limb volume due to ambulation, and can in fact result in an increase in residual limb volume. Wayne J. Board, “Below-knee Amputee Residual Limb Responses to Vacuum-assisted and Suction Socket Conditions”, St. Cloud State Univ., October, 2000.
A second study, also conducted under the direction of the Applicant/Inventor in partial fulfillment for a Masters degree has shown that interface pressures, measured at five points between the surface of the residual limb and the liner, were quite different between a standard total surface-bearing socket and a vacuum-assisted socket. Tracy L. Beil, “Interface Pressures During Ambulation using Suction and Vacuum-assisted Prosthetic Sockets”, St. Cloud State Univ., July, 2001. The vacuum-assisted socket created significantly lower positive impulse and peak pressures during the stance phase of ambulation. Ibid. The impulse, average, and peak negative pressure values calculated for the swing phase of ambulation were significantly greater in magnitude with the vacuum-assisted socket. Ibid. It is thought that lower pressures seen during both stance and swing phases using the vacuum-assisted socket reduce the fluid forced out and increase the amount of fluid drawn into the limb, thereby preventing volume loss. Ibid.
Previous to the above two studies, the present inventor disclosed, in application Ser. No. 09/492,406 (now issued U.S. Pat. No. 6,508,842 and herein incorporated by reference), that application of vacuum to an artificial limb socket can prevent the loss of residual limb volume.
Ambulation causes the shape of the residual limb, the temperature within the prosthetic socket, and pressures within the socket to change. There is a need for a device to warn the patient that certain levels have been exceeded.